Field of the Invention
The present invention generally relates to a heat radiating plate and a method for producing the same. More specifically, the invention relates to a heat radiating plate for an electronic part mounting substrate, and a method for producing the same.
Description of the Prior Art
Heat radiating plates for electronic part mounting substrates are required to have good thermal conductivity since they are required to efficiently radiate heat generated from electronic parts, such as semiconductor elements.
As such a heat radiating plate, there is widely used a heat radiating plate of copper or a copper alloy having good thermal conductivity. Such a heat radiating plate is generally produced by press-forming a strip of copper or a copper alloy by means of a progressive die, and then, by carrying out a treatment, such as nickel plating, if necessary (see, e.g., Japanese Patent Laid-Open No. 2007-220702).
Such a heat radiating plate for an electronic part mounting substrate more greatly shrinks than the electronic part mounting substrate to warp when it is bonded to the electronic part mounting substrate by soldering. For that reason, it is known that the heat radiating plate is previously caused to warp in the opposite direction (to have opposite warpage) before solder joint (see, e.g., Japanese Patent Laid-Open No. 2007-88045).
If the heat radiating plate is produced by press-forming by means of a progressive die, the opposite warpage of the heat radiating plate can be carried out by a series of plastic deformations during the correction of shape by means of a leveler and/or during the press-forming. However, a heat radiating plate having a high thermal conductivity of not less than 250 W/m·K is relatively soft (the Vickers hardness Hv thereof is not higher than 135). If the opposite warpage of such a soft heat radiating plate is carried out by a series of plastic deformations during the correction of shape by means of a leveler and/or during the press-forming, when a strip to be the material of the heat radiating plate is progressively fed (intermittently fed), the variation in residual stress is caused, so that it is difficult to stably cause the strip to warp.